The present invention relates generally to aspirating face seals between rotor and stator assemblies and, more particularly, to an aspirating face seal having retraction springs.
Aspirating face seals minimize leakage of a fluid, such as compressed air or combustion gases, by restricting flow between an area of high pressure and an area of low pressure. Aspirating face seals control leakage by compensating for variations in the gap which may exist between a rotor and stator. Such seals have been disclosed for use in rotating machinery, including, but not limited to, gas turbine engines used for power generation and for aircraft and marine propulsion.
Fluid leakage through gas turbine engine seal assemblies may significantly increase fuel consumption and adversely affect engine efficiency. Additionally, fluid leakage may cause damage to other components and/or increase overall engine maintenance costs. Because of the location of the seal assemblies and/or the operating environment, at least some known seal assemblies may deteriorate over time.
Some embodiments of aspirating face seals have the rotor configured as oppositely facing rotatable first and non-rotatable second seal elements. The rotatable first seal element is attached to, or is a monolithic portion of, the rotor. Likewise, such seals typically have the stator supporting the non-rotatable second seal element which is attached to, or a monolithic portion of, a slider. Retraction springs, typically coil springs, are used to separate or retract the rotating first and the non-rotating second seal elements during low or no power conditions. The non-rotatable second seal element is mounted on the slider supported by the stator. Examples of such aspirating face seals are disclosed in patent applications from General Electric Company in Docket Numbers 279249 and 280429, filed in INDIA, assigned to the present Assignee the General Electric Company, and incorporated by reference. Docket Number 279249 is entitled “ANTI-CONING ASPIRATING FACE SEAL” and was filed in India on Apr. 14, 2016 with a Serial Number 2016/41013072. Docket Number 280429 is entitled “ASPIRATING FACE SEAL TOOTH CONFIGURATION” and was filed in India on May 11, 2016 with a Serial Number 2016/41016504.
U.S. Pat. No. 6,676,369 to Brauer, et al., issued Jan. 13, 2004, and entitled “Aspirating Face Seal with Axially Extending Seal Teeth”, discloses a gas turbine engine aspirating face seal including a rotatable engine member and a non-rotatable engine member and a leakage path therebetween. Annular generally planar rotatable and non-rotatable gas bearing face surfaces circumscribed about a centerline are operably associated to the rotatable and non-rotatable engine members respectively. Radially inner and outer tooth rings axially extend away from a first one of the rotatable and non-rotatable gas bearing face surfaces across the leakage path and towards a second one of the gas bearing face surfaces. An auxiliary seal includes an annular restrictor tooth extending radially across the leakage path from a second one of the rotatable and non-rotatable gas bearing face surfaces towards the first one of the rotatable and non-rotatable gas bearing face surfaces. Coiled springs are utilized to separate the gas bearing face surfaces.
Known seal designs have also included an aspirator tooth extending from the stator axially across, and radially inward of, the air dam with the aspirator tooth having a tip spaced apart from and proximate the rotor. It is also important to note that aspirating face seal technology uses phrases such as “air bearing”, “air dam”, and “air flow”, wherein it is understood that the word “air” is used to describe the working fluid of the seal. The working fluid of an aspirating face seal can include, without limitation, compressed air, combustion gases, and/or steam. Note, that an aspirating face seal is a non-contacting seal in that the first and second parts of the seal are not intended to touch but may for short periods of time during which they experience what are known as rubs.
The slider has sliding interfaces to guide the non-rotating seal member mounted on the stator or support. These interfaces allow the non-rotating seal member to translate axially but prevents rigid body motion in the radial direction or rotation in the circumferential direction. These sliding interfaces also allow a small amount of tilt to accommodate misalignment between the rotating and non-rotating portions of the seal. These sliding interfaces are subject to wear. It is desirable to reduce or eliminate wear of the sliding interfaces.